A memory system may employ a memory controller through which a component (e.g., system processor) of an associated system gains access to several memory devices. For example, a memory controller may be adapted to control the operation of and provide access to the memory devices by communicating with the memory devices over a signaling path (e.g., signal traces of a printed circuit board). In some implementations such a signaling path is directly coupled to several discrete memory devices (e.g., DRAM integrated circuits). In other implementations a signaling path may be coupled to one or more memory modules, each of which may include one or more memory devices.
A signaling path may be routed in a multi-drop/fly-by fashion between the memory controller and the memory devices. For example, a signaling path comprising printed circuit board traces may be routed from the memory controller to a first one of the memory devices and then to a second one of the memory devices and so on. In practice, such a configuration may negatively impact the rate at which high speed signals may be sent over the signaling path and/or the power consumption of the memory system. For example, when operating at relatively high signaling rates, any discontinuity in the signaling path (e.g., a discontinuity at the end of the signaling path) may cause signal reflections that interfere with the transmission of another signal (e.g., a subsequently transmitted bit) along the signaling path. Consequently, parallel termination resistors may be employed at the end of the signaling path in an attempt to eliminate the discontinuity at that point and thereby reduce any associated signal reflections. The use of such parallel termination resistors may, however, increase the power consumption of the memory system due to the resulting current flow through these resistors.
In accordance with common practice the various features illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus or method. Finally, like reference numerals may be used to denote like features throughout the specification and figures.